That’s not really the case (grey), but it’s what happens by default.

The K does stand for blacK. The four are mixed to create a richer black than the black alone would provide - which conveniently looks better and uses more ink.

The software and printer are more than capable of not using “rich black” outside of images, but even the solid black ink will look muted to people used to seeing the mud from all four colours in their 12 point Times New Roman.

A sad state really that in 2024 we still have an ink racket.